Voltage supply and control system



Feb. 5, 1963 R. v. SMITH VOLTAGE SUPPLY AND CONTROL SYSTEM 2Sheets-Sheet 1 Filed May 1, 1961 INVENTOR. RAYMOND V. SMITH BY Mme I53Amplifier Agent Feb. 5, 1963 Filed May 1 R. V. SMITH VOLTAGE SUPPLY ANDCONTROL SYSTEM ground INVENTOR. RAYMOND V. SMITH Y it t This inventionrelates to a voltage supply and more particularly to a voltage supplyuniquely adaptable to a photomultiplier device.

in photomultiplier devices it is mandatory that the over-allmultiplication factor be kept constant irrespective of load or theintensity of bombardment of the photocathode thereof. Since the latterstages of photomultipliers draw relatively large currents it isnecessary that these stages be supplied by a low impedance source. Theconventional method for doing this is by means of a voltage dividernetwork consisting of a plurality of series connected resistors whichare supplied power by a high voltage D.C. source. By this method it isnecessary that the resistance of the resistors connected to these stagesbe relatively low so when varying currents are drawn, the chan e involtage drop across the associated resistor is small and the voltageapplied to each of these stages there fore remains relatively constant.The primary disadvantage of a resistive network of this type is, withthe high voltages necessary for operation and the low networkresistance, there is large power consumption which necessitates a largeand frequently complex power source with corresponding voltage controldifficulties.

The present invention obviates the disadvantages of these prior voltagesupply devices by providing a unique voltage supply and control systemthat requires rela 'vely small currents and maintains a constantover-all multiplication factor irrespective of photomultiplier load. This is accomplished by converting B+ power into AC. power by means of anoscillator and applying the AC. power to a diode-capacitor voltagemultiplier network thereby providing a high voltage D.C. voltage source,each stage of which has consecutive integral multiples of the oscillatoroutput voltage. The voltage multiplier network has a low outputimpedance and each stage is individually connected through a filtercircuit to separate dynodes of the photomultiplier. Eifective filteringand impedance characteristics are realized since the cynodes at the lowvoltage stages of the voltage multiplier network draw more current thanthe dynodes at the high voltage stages where the AC. components to befiltered are relatively large and require relatively large the voltagemultiplier output. Control of the system is realized by sampling thevoltage at the last dynodewhich reflects both variations in B+ supplyvoltage and photomultiplier lead. This control reflects photomultiplierload by sensing the current drawn by the last dynode and it is thereforepossible to maintain a constant over-all photomultiplier multiplicationfactor by varying the relative potentials between individual dy nodes asa function of photomultiplier load. The last dynode potential is appliedto a zener diode which is connected to a transistor for controlling theseries impedance between the 13+ supply and the input to the oscillator,to maintain the dynode at the breakdown voltage of the selected zenerdiode. Temperature compensated is realresistors in series with u l tentized by employing a thermistor in series with the selected zener diode.

Accordingly, an object of the present invention is to provide a stable,high voltage supply requiring very little power.

Another object of the present invention is to provide a stable, highvoltage supply for supplying a photomultiplier device the necessarydiscrete D.C. voltages.

Still another object of the present invention is to pro vide a stablevoltage supply for a photomultiplier wherein the voltage is supported bya capacitor-diode network.

A further object of the present invention is to provide a voltage supplywhich has a plurality of individual power supplies connected toindividual dynodes of a. photomultiplier.

A still further object of the present invention is to provide a voltagesupply for a photomultiplier device which maintains the over-allmultiplication factor or" the photomultiplier constant irrespective ofvariations of 13+ supply voltage and photomultiplier load.

A still further object of the present invention is to provide a D.C.voltage supply, filter and current bleeder network wherein the voltageacross each component is maintained at a minimum thereby minimizingcomponent failure.

The specific nature of the invention, as well as other objects, uses andadvantages thereof, will clearly appear from the following descriptionand from the accompanying drawing in which:

FIGURE 1 is a schematic illustration of the voltage supply and controlcircuit of the present invention.

FIGURES 2A, 2B and 2C are curves illustrating the operation of thedevice shown in FIGURE 1.

in FIGURE 1 is schematically illustrated the circuit of the presentinvention wherein reference numeral ll generally denotes the oscillator,reference numeral l2 generally denotes the D.C. voltage multiplier,reference nu meral 13 generally denotes the photomultiplier device andreference numeral 14 generally denotes the control system.

Power for operation of the system is obtained from a D.C. source denotedas 13+ and is applied to the input of oscillator 11. Resistor l5 andcapacitor 17 are provided to filter the A.C. component which may besuperposed on the 8-}- power supply. As will hereinafter becomeapparent, accurate control of the 8+ power sourc is unnecessary becauseof the unique compatibillties of the DC. voltage multiplier,photomultiplier and control system. it has been found that a constantphotomultiplier multiplication factor is realized with B+ voltagevarying from about 22 to about 35 volts. This is a high ly advantageousfeature since the photomultiplier may then be battery operated over arelatively long period of time.

Gscillator 11 is of the push-pull type and includes transistor l9,transistor 21, transformer 22 including windings 23, 2dand 25, and iscontrolled by transistor 27. Upon the initial application of B+ power tothe oscillator input, either transistor 19 or transistor 21 will conductmore rapidly than the other since two transistors are never entirelysymmetric. Assuming transistor 19 conducts more rapidly than transistor21, then the rate of change of current from point d to point e isgreater than from point d to point 0 of winding 24. Point 0 will thusbecome positive with relation to point e, as illustrated,

since voltage drop is proportional to rate of current change across aninductive load. Winding 25 is wound with relation to winding 24 so thefiux induced by increasing rate of current flow from point d to point 1:causes point It to be positive with relation to point f of winding 25.Since point h is driven positive, transistor 19 will be driven togreater conduction and since point f is driven negative, transistor 21will be driven to lesser conduction. Considering only transistor 19,initially the rate of change of current from point d to point e ispositive, and as the base of transistor 19 is driven more positive andreaches saturation, the rate of change of current from point d to pointe reverses. With this reversal of rate of current change, the fluxinduced in winding 25 is reversed and point f will be driven positivewith relation to point It. As this occurs, transistor 21 will becomeconducting and transistor 19 will become nonconducting and point e willbecome positive with relation to point 0. i As transistor 21 reachessaturation, the rate of change of current from point d to point creverses and point It becomes positive with relation to point f.Therefore, transistor 19 becomes conducting and transistor 21nonconducting and the above described sequences will be repeated.Therefore, there is free running oscillation at a frequency which isestablished by the oscillator parameters. It should be noted that whenthe base currents of transistors 19 and 21 are large, the transistorswill not saturate untilthe collectors approach ground potential.However, when thebase currents are small, the transistors will saturateprior to the collectors reaching ground potential. These base currentsare controlled by the effective collector-emitter resistance oftransistor 27 the operation of which will hereinafter be described.Therefore, by varying these base currents, the peak to eak voltage inwinding 24 is varied and as a result the peak to peak voltage oramplitude of the signal induced in winding23 is varied.

In FIGURE 2A are shown the voltage signals at the various pointsindicated in FIGURE 1 during that period when large base currents arepermitted to be drawn by transistors 19 and 21. In FIGURE 2B are shownthe voltage signals at the same points when large base currents are notpermitted to be drawn by these transistors. Curves A and B of FIGURE 2Crepresent the voltage induced in winding 23 during the operatingconditions shown in FIGURE 2A and 213, respectively. Winding 23 may havethe polarity indicated or it may be reversed by reversal of thedirection of winding on the associated core. It should be noted themaximum peak-to-peak amplitude of the signals at points c and e islimited by the voltage and will have a maximum amplitude ofapproximately twice the B+ potential. Consequently, for a predeterminedturn ratio between windings 23 and 24, the induced voltage in winding 23is likewise limited. However, the turn ratio is selected so slightlymore than 200 volts peak-to-peak may be obtained with about 22 volts3-]- power and still realize the necessary current for successfuloperation. It is to be understood that various turn ratios and 13+voltages may be employed to provide sufficient voltage and current tothe particular load which is being supplied by DC. voltage multiplier12. It is also to be understood that other types of oscillators may beemployed so long as they remain compatible with the hereinafterdescribed DC. voltage multiplier and control system.

The output of winding 23 of oscillator 11 is applied to the input of DC.voltage multiplier 12 which includes capacitors 29 through 40, diodes 41through 64, capacitors 67 through 78, resistors 80 through 91, resistors93 through 104, capacitors 105 through 116 and capacitors 118 and 119.Assuming the peak-to-peak voltage output of the oscillator isfrom +100to -100 volts, then capacitor 29 will initially charge to ---100 voltssince diode 41 permits electrons to pass only in the direction to bringabout this negative charge. A steady state condition is realized afterthis initial charge on capacitor 29 and no current will pass throughdiode 41 when the anode thereof is negative with respect to ground.Therefore, the oscillator input to capacitor 29 is superposed on thenegative charge thereon with a resultant signal varying from ground to200 volts at point m of FIGURE 1. Since the anode of diode 42 ispositive with respect to point m there is flow of electrons to capacitor67 with a resultant steady state voltage at point 0 of -200 volts. Thepotential applied to capacitor 36, which is analogous to capacitor 29,varies from 0 to -200 volts (point m) and the potential applied to thecathode of diode 43, which is analogous to diode 41, is 200 volts (pointo). In the same manner as described with relation to capacitor 29 anddiode t3, the potential at point p will vary between 200 and -4G0 volts.The potential at point r will realize a steady state value of 4G() voltsin the same manner as was de scribed with relation to diode 42 andcapacitor 67. This same process is continued through capacitorsv 31through 41 diodes 44 through 64 and capacitors as through '73 so thesteady state potentials applied to the dynodes of photomultiplier 13 aremultiples of 200 volts, and the photocathode thereof is at a potentialof .-2,400 volts It is to be understood that various numbersof'multiplication stages, and various values of voltagesper stage, maybe used in particular applications, and the .twelve'sta'ge voltagemultiplier shown in FIGURE 1 is consideredito be only exemplary.

Fhotomultiplier 13 includes photocathode which emits electrons whenlight impinges thereupon. The num-' ber of electrons emitted arerelatively few and are accelerated by the field created by thediiferential potential between photocathode 12d and'grid 121. Dynode 122further accelerates and attracts these electrons and upon theircollision therewith results in the release of a greater number ofelectrons which is some multiple of the number of colliding electrons.This multiplication of electrons is continued by the remaining dynodes.Assuming an individual dynode multiplication factor of four and that tendynodes are employed, as shown, there is an overall current or electronmultiplication factor of 4 or ap-' proximately one million. It cantherefore be seen the current drawn from voltage supply 12 by dynodes122 through 131 progressively increases and dynode'131 draws very largecurrent as compared with dynode 122', photo-' cathode 121 or grid 121.

As previously indicated, in photomultiplier devices it is necessary thatthe over-all multiplicationfactor of the photomultiplier be keptconstant irrespective of load or the intensity of bombardment of thephotocathode thereof. Since the latter stages of the photomultiplierdraw relatively large currents it is necessary that a low impedancesource supply these stages; As previously indicated, the conventionalmethod for doing this is by means of a voltage divider networkconsisting of a plurality of series connected resistors which areconnected to a high voltage D.C. source. However, it is necessary thatthe resistance of the resistors connected to the latter dynodes berelatively low so when varying currents are drawn by these dynodes thechange in voltage drop is small and the vol age on each dynode thereforeremains relatively constant In order that ap-' proximately uniformvoltage division be obtained, it is.

irrespective of the variation of current.

necessary that the over-all resistance of the network be relatively low.In view of the low resistance network and the high voltages necessaryfor operation, it can be seen there is large power consumption whichnecessitates a large and frequently complex power source with correspo d'm v age control difficulties.

It should be particularly noted that an.A.C. signal, at.

a frequency coresponding to the oscillator frequency, is superposed onthe DC. potential of capacitors 67 through 78. This A.C. component atpoint 0 of voltage multiplier 12 is relatively small; however, thissmall A.C.

component is amplified by the stages of the DC. voltage multiplier andat point s the A.C. component will be relatively large. It is desirableto filter the A.C. component from voltage applied to the dynodes bymeans of resistors 93 through 104 and capacitors 105 through 116. Sincethe A.C. components at points s and t are large, it is necessary thatresistors 1M and 192 have large values of resistance and since the A.C.component at points 0 and r are relatively small, the resistance ofresistors 93 and 94 may be relatively small. It can therefore be seenthat voltage multiplier 12 is uniquely adaptable to a photomultipliertube since at the photocathode end, the dynode current is small and itis possible to employ a large resistor in series with the voltage supplyto filter the large A.C. component; whereas, at the anode end, where thedynodes draw large currents, the A.C. component may be etfectivelyfiltered by a small resistor. Consequently, over-all efiective filteringis obtained and the voltage on each dynode remains relatively constantirrespective of load since the source impedance is small for dynodesdrawing large currents and large for dynodes drawing small currents.

It should be particularly noted that the capacitance of capacitor 116could be decreased to a value equivalent to the total series capacitanceof capacitors 105 through 116 and then connected directly to ground sofiltering of the large A.C. component on the photocathode end could berealized by means of resistor 1M and this ground connected capacitor.Likewise, capacitors 166 through 115 could be connected directly toground provided the capacitance of each is decreased to a valuecorresponding with the remaining series capacitance. By utilizing afilter system of this type, the voltage across the filter capacitorswould be much greater than the individual stage voltage and consequentlycapacitor failure would more readily occur. It can be seen that byemploying the capacitors in series as shown in FIGURE 1 that efiectivecapacitance of the capacitors at the photocathode end is realized, andyet, the voltage across each of these capacitors is limited to arelatively small value as determined by the muimum peak-topeak voltageof the oscillator output.

It has been found by employing the above described filter system, with aten volt photomultiplier output, the A.C. component superposed on thisten volt output is only about 50 millivolts peak-to-peak, whereas, whenthe filter network is not employed, the A.C. component is increased toapproximately one-half volt peak-to-peak.

Capacitors 118 and 119 may be used to provide additional filtering andare dependent upon the particular photomultiplier employed. The valuesof these capacitors may be determined empirically; however, it is to beunderstood that they are not critical for effective opera tion of thepresent invention.

It should be particularly noted that power required by this scheme isvirtually only that drawn by the dynodes and there is therefore nowasted power as is the case in resistance network devices. Since thepower consumed is very small it is possible to employ a small 13-]-power supply and utilize an oscillator and control system as hereindescribed. In addition, since linearity is poor in resistance networkphotomultiplier power supplies, to provide control it has been necessaryto employ a high impedance divider across the power supply and parallelwith the entire resistance network. Since linearity of the power supplyof the present invention is highly stable under varying loads, voltagecontrol is realized by sampling a single stage as will hereinafter bemore completely described.

The current drawn by the photomultiplier from capacitors 67 through 78is relatively small and effective control may be therefore preventedsince electrical charge would remain on these capacitors particularlyduring low load operation. That is, if the hereinafter described controldetected the over-all multiplication factor as being too large, theamplitude of the oscillator output signal would be reduced. However,capacitors 67 through 78 would not rapidly follow this reduced voltagesince the current drawn therefrom would be negligible. To provide rapidcontrol, resistors 80 through 91 are provided to discharge capacitors 67through 78 to ground. The values of resistors 80 through 91 are selectedso the current discharged from each of capacitors 67 through 78 isuniform. This is accomplished by series connecting these resistors toground so the etfective resistance is large at the photocathode end andsmall at the anode end. This same uniform discharge rate could beaccomplished by connecting each of resistors 81 through 91 directly toground and increasing the value of each to correspond with the efiectiveresistance of the series string. However, this latter method has thedisadvantage of having the entire stage voltage across each resistor andconsequently resistor failure would more readily occur.

The primary purpose of a photomultiplier control system is to maintain aconstant over-all multiplication factor which is independent of dynodeload or light energy input to the photocathode, and B+ voltage. Aspreviously indicated, in prior systems this control has beenaccomplished by regulating the power supply by the voltage across ashunting resistor in parallel with the resistance network. Accuratevoltage control in these prior systems has been very difiicult torealize since it is inherently ditficult to provide accurate voltagecontrol of power supplies that have large current requirements. Inaddition, these prior systems have not compensated for voltagedeviations due to variations of current drawn by the individual dynodes.

The present invention provides a unique voltage control system whichcorrects for both variations in supply voltage as well as variations incurrent drawn by the dynodes. Voltage control is realized by sensing thevoltage of dynode 131 with respect to ground. It can be readily seenthat when dynode 131 is not drawing current that this control voltage isthe voltage on capacitor 67. Since the voltage output of oscillator 11,and therefore the voltage on capacitor 67, would, without the controlsystem, vary with variations of 13+ voltage, this voltage control isresponsive to variations of B+ voltage. addition, the voltage On dynode131 will also reflect current drawn by this dynode because there is aresultant voltage drop across resistor 93. Since the voltage of eachsuccessive stage of voltage multiplier 12 is acon secutive integralmultiple of the first stage, control of the first stage will ofnecessity result in control of the remaining stages.

In operation, when dynode 131 draws current, the voltage drop acrossresistor 93 causes an amplitude increase of the signal from oscillator11, since the control system requires that the oscillator maintain thevoltage constant on dynode 131. Due to the multiplicationcharacteristics of voltage multiplier 12, the dynodes at thephotocathode end of the photomultiplier will have a greater voltageavailable per stage, and consequently a greater multiplication factorthan the dynodes at the anode end. This is because the dynodes at thephotocathode end draw considerably less current than those at the anodeend with resultant smaller voltage drops across the filter resistors inseries with the dynodes. The value of resistor 93 is selected so anearly flat over-all gain factor is realized by the photomultiplierduring all load conditions. That is, during large loads the potentialdifference between dynodes 122 and 123 may be 210 volts and thepotential difierence between dynodes 13d and 131 may be only volts andduring small loads may be 201 and 199 volts, respectively. In thismanner the over-all photomultiplier gain is maintained at a nearlyconstant value irrespective of load. Obviously, if only a voltage andnot a current responsive control were employed, the over-allmultiplication factor would decrease with increased load since thepotential difference between dynodes 12.2; and 123 would be about 200volts whereas 7* the potential difference between "dynodes 13d and 131would be about 190 volts due to the largevoltage'drop across resistor93. For purpose of illustration these above potential changes 'have beenexaggerated and 'in practice are considerably less. Even withoutfilterresistors 93 throughlihtfitis desirableto employ'a current responsivecontrol to maintain 'a constant multiplication'factor since each stageof the DC. voltage multiplier has 'a finiteoutput resistance whichcan'never be reduced to zeror Control is accomplished by applyingthepotential of dyno'de' 131 in series with thermistor 133' andzener'diojde 135' to the base of transistor 27. Thermistor133, zenerdiode 135 and capacitor 137 and 13%, whichshunt zener diode135, areinterdependent and zener diode 135 is selected .to bring about theparticular value of photomultiplier gain desired. These components maybe prepack- B-'1'- voltage'and the operatingpoint of 'zener diode 135isvery accurately determined.

Forrpurpo'seof description, it is assumed that Lzener diodef=135 hasabreakdown'voltagerof 200 volts: In' addi tion, transistor 27'is=seleetedto have a very large current' gain and the base thereof draws verylittlecurrent when conducting;- Upon the application of 13+ power, zenerdiode 135' offers infinite impedance and thebas'e of tra nsister 27 willbe driven positive and-into a saturation state;

Since trwsistor27 is saturated, the emitter-collector impedancethere'ofzis minimum and maximum B+ voltage is available'to thebases oftransistors 19 and 21',"as shown by-curvesff and fhfof"FIGURE-"2A. Aspreviously explained, oscillatorxll will then provide maximum voltageoutput. D-.C.'.voltage multiplier 12 is'very rapidly charged since itdraws very little currentand the dynode's very rapidly acquire theirinteger multiple potentials of 209*ivoltsr When dynode 131 has a voltagevery slightly greater than 200 volts, zener diode1135' rapidly startscon-- ducting, When zener diode. 135 conducts, the'curren'tfrom the baseof transistor is.shun'tedthrough zener diode 135,. thermistor 133,resistors-93 and 8t) and diodes 42 and 41 toground. Since this shuntingpath provides a much smaller impedance than the path through transistors27, 19 and 21 and resistor 147 to ground, .the voltage at the base oftransistor 27 very closely approaches ground when zener diode 1355becomes conducting. Therefore, since the base of transistor. is drivento ground, the col-.

lector-emitter impedance thereof is. rapidly increased thereby greatlyreducingthe. current available to the bases of transistors 19 and 21, asshown by curve f and h of FIGURE 2B. Inactual operation the peak-to-peakvoltages shown in FIGURElB would approach zero when zener diode 135'conducts; Ifthe voltage on dynode 131 then reduces very slightly below200 volts, zener diode 13S becomes non-conducting and the potentialapplied to the base of transistor 27 increases thereby greatly reducingthe collector-emitter impedance thereof and results in large currentbeing applied to the bases of transistors 19 and 21 and therebyproviding maximum voltage output from oscillator 11 and increasing thevoltage on dynode 131 back to .200 volts. It should be particularlynoted that since voltage multiplier 12 draws very little current andtransistor 27 has a high base impedance and: draws very little current,the voltage variation at the base of transistor 27 varies from onlyabout .1 volt to about ground potential during normal operation. It cantherefore be seen that the response rate of the control system is veryrapid and maintains voltage multiplier 12 within extremely closetolerances as determined by Therefore, the current -for this variation.

8 the selected breakdown voltage of zener diode 135. The above'describedoperation is related to a 200 volt control which assumes that oscillator11 provides at leasta 2G0 peak-to-peak voltage output. Obviously if 200volt'control were necessary, the p'eak-to-peak voltage output ofoscillator 11 would be selected to have a value considerably greaterthan 200 volts inorder to realize rapid control. It has been found thatan oscillator providing a maximum peak-to-peak voltage output of about200 volts,

provides very satisfactory control for dynodeto-dyuode voltages up toabout 175' volts. 7

It is to beunderstood that voltage control from slightly greater thanzero volts to many thousand volts may readily be obtained by the abovedescribed scheme and may be accomplished merely byselecting difierentoscillator parameters; zener diodes or employing several in series, B+power supply, DC. voltage multiplier parameters, 'etc., and still remainwithin the scope Of'ihiS'iHVCl'b' tion.

Capacitors 137 and 138 functionas'xa bypass for; the high frequencynoise inherentin zener diode 135' and are selected to match theparticular diode employed. In addition, the time constant of capacitors13'? and139 and the resistance of thermistor 133 'are seleeted "sotheover all feedback loop will operate stably at a variety ofoper-* atingconditions and thereby obviatehunting;

Since the breakdown voltage-characteristic 'ofzener diode 135 variesdirectly with'temperature, thermistor 133 may be provided in" seriestherewtih' to'compensate' Thermistors have a negative 'tem-' p'e'raturecoefiicient and the resistance thereof therefore varies inversely withtemperature. The charactristics of thermistor 133 are selected toinversely match thecharacteristics of zener diode 135 such that as thebreakdown voltage acrossthe zener diode increases withtem perature, theresistance and corresponding voltage'drop across-thermistor 1'33decreases by the same amount; T 0 illustrate, if it is'desired 'tomaintaindynode 7131 'at volts, the breakdown voltage of zener diode" maybe selected at 97 /2 volts and the voltage drop across" thermistor 133at 2 /2 volts, both at room temperature;

Therefore, when dynode'131. is at 100 volts, 97 /2 volts will appear atthe anode of zener diede 13 5 and it will If the temperature would" riseto'about 35 C., the breakdown voltage of zener therefore startconducting.

diode 135 would raise to about 98% and the resistance of thermistor 133would decrease so the voltage drop across the thermistor would be about1 /2 volts. Therefore, zener diode 135 would again start'conducting whendynode 131" was at 100 volts. In this manner the control system providesaccurate voltage regulation'independent of temperature variations. Thereare other relatively, minor temperature coefficie'nts in the powersupply and oscillator and in practice, thermistor 133 is empirically.

selected to compensate for these as well as the temperature coeihcientof zener diode'135.

The output ofv the above described system istaken; from anode 151 ofphotomultiplier 13 which is applied" tothe input of amplifier 153 whichprovides avolta'ge' outputindicative of the rate of bombardment ofphotocathode 120.

sidering such factors asv load, voltage requirements, im-

pedance characteristics, etc. Likewise, substantial de- It is desirablethat amplifier 153 have a' large input impedance since the anode currentis rela-- parture may be made when different photomultiplier voltagesare required.

Components: Values 16 20 ohms. 17 8 microfarads. 29-40 .01 microfarad.67-78 .01 microfarad. 80-91 megohms. 93 10,000 ohms. 94';- 20,000 ohms.95' 30,000 ohms. 96 39,000 ohms. 97 51,000 ohms. 98 62,000 ohms. 9968,000 ohms. 100 82,000 ohms. 101 91,000 ohms. 102 100,000 ohms. 103110,000 ohms. 104 120,000 ohms. 105-116 .01 microfarad. 118-119 .01microfarad. 133 10,000 ohms at room temperature. 135 100 volts. 137-138.01 microfarad. 143 13,000 ohms. 144 43,000 ohms. 146 11 volts. 1471,000 ohms. B-l- 22-35 volts.

In view of the foregoing, it can be seen the present invention providesa small lightweight and highly reliable D.C. high voltage supply. Inaddition, it is uniquely adaptable for use in conjunction with aphotomultiplier in that control is a function of 3-]- power,photomultiplier load, and temperature, and therefore maintains aconstant over-all photomultiplier multiplication factor irrespective ofvariation of these conditions. Furthermore, reliability of theindividual components is enhanced since the voltage across eachcomponent is maintained at a minimum.

It is to be understood in connection with this invention that theembodiment shown is only exemplary, and that various modifications canbe made in construction and arrangement within the scope of theinvention as defined in the appended claims.

What is claimed is:

l. The combination of a photomultiplier device and a power supply, saidpower supply comprising a diodecapacitor voltage multiplier networkhaving a plurality of discrete D.C. voltage output stages and a lowoutput impedance, each of said output stages being individuallyconnected to separate dynodes of said photomultiplier device, wherebythe total power required by said power supply is about the same as thetotal power supplied by said power supply to said dynodes.

2. The combination of a photomultiplier device and a power supply saidpower supply comprising a direct current source operatively connected toan oscillator the output of which is operatively connected to the inputof a D.C. voltage supply, said D.C. voltage supply comprising adiode-capacitor voltage multiplier network having a plurality ofdiscrete D.C. voltage output stages and a low output impedance, each ofsaid output stages being individually connected to separate dynodes ofsaid photomultiplier device, whereby the total power required by saidpower supply is about the same as the total power supplied by said powersupply to said dynodes.

3. A power supply device comprising a direct current source operativelyconnected to the input of control means, the output of said controlmeans operatively connected to the input of an oscillator, the output ofsaid oscillator operatively connected to the input of a DC. voltagesupply, said D.C. voltage supply comprising a diode-capacitor voltagemultiplier network having a plurality of discrete D.C. voltage outputstages, said control means responsive to the voltage at one of saidstages for controlling the output current from said control means tomaintain the voltage on said stages at approximately constant values.

4. A power supply device comprising a direct current source connected tothe collector and base of a transistor, the emitter of said transistoroperatively connected to the input of an oscillator, the output of saidoscillator operatively connected to the input of a voltage supply havinga plurality of discrete D.C. voltage outputs, one of said discrete D.C.voltage outputs operatively connected to the anode of a zener diode, theoutput of said zener diode operatively connected to the base of saidtransistor, whereby the voltage at said one of said discrete D.C.voltage outputs is maintained at the breakdown voltage of said zenerdiode.

5. The combination of a photomultiplier device and a power supply, saidpower supply comprising a direct current source connected to thecollector and base of a transistor, the emitter of said transistoroperatively connected to the input of an oscillator, the output of saidoscillator operatively connected to the input of a voltage supply havinga plurality of consecutive stages having consecutive integral multipleD.C. voltage outputs, each of said consecutive stages operativelyconnected to consecutive dynodes of said photomultiplier device, afilter network including a plurality of resistors individually connectedin series between each stage a respective dynode, one of said dynodesoperatively connected to the anode of a zener diode, the output of saidzener diode operatively connected to the base of said transistor,whereby the voltage on said dynodes are varied as a function of the loadof said photomultiplier to maintain a constant over-all photomultipliermultplication factor irrespective of load changes of saidphotomultiplier.

6. The combination of an electron discharge device and a power supply,said electron discharge device being of the electron multiplier type,having at least a plurality of dynodes with secondary electron emittingcharacteristics and an anode, output means connected to said anode, saidpower supply comprising a diode-capacitor voltage multiplier networkhaving a plurality of discrete D.C. voltage output stages, each of saiddynodes of said electron discharge device being individually connectedto a separate output stage of said diode-capacitor voltage multipliernetwork of said power supply.

7. The combination of a photomultiplier device and a power supply, saidpower supply comprising a diode-capacitor voltage multiplier networkhaving a plurality of discrete D.C. voltage output stages and a lowoutput impedance, each of the dynodes of said photomultiplier devicebeing individually connected to a separate output stage of said powersupply, whereby the total power required by said power supply is aboutthe same as the total power supplied by said power supply to saiddynodes.

References Cited in the file of this patent UNITED STATES PATENTS2,535,811 Oliver Dec. 26, 1950 2,737,625 Felici Mar. 6, 1956 2,889,512Ford et al. June 2, 1959 3,003,065 Ketchledge Oct. 3, 1961 3,009,093Seike Nov. 14, 1961

5. THE COMBINATION OF A PHOTOMULTIPLIER DEVICE AND A POWER SUPPLY, SAIDPOWER SUPPLY COMPRISING A DIRECT CURRENT SOURCE CONNECTED TO THECOLLECTOR AND BASE OF A TRANSISTOR, THE EMITTER OF SAID TRANSISTOROPERATIVELY CONNECTED TO THE INPUT OF AN OSCILLATOR, THE OUTPUT OF SAIDOSCILLATOR OPERATIVELY CONNECTED TO THE INPUT OF A VOLTAGE SUPPLY HAVINGA PLURALITY OF CONSECUTIVE STAGES HAVING CONSECUTIVE INTEGRAL MULTIPLED.C. VOLTAGE OUTPUTS, EACH OF SAID CONSECUTIVE STAGES OPERATIVELYCONNECTED TO CONSECUTIVE DYNODES OF SAID PHOTOMULTIPLIER DEVICE, AFILTER NETWORK INCLUDING A PLURALITY OF RESISTORS INDIVIDUALLY CONNECTEDIN SERIES BETWEEN EACH STAGE A RESPECTIVE DYNODE, ONE OF SAID DYNODESOPERATIVELY CONNECTED TO THE ANODE OF A ZENER DIODE, THE OUTPUT OF SAIDZENER DIODE OPERATIVELY CONNECTED TO THE BASE OF SAID TRANSISTOR,WHEREBY THE VOLTAGE ON SAID DYNODES ARE VARIED AS A FUNCTION OF THE LOADOF SAID PHOTOMULTIPLIER TO MAINTAIN A CONSTANT OVER-ALL PHOTOMULTIPLIERMULTIPLICATION FACTOR IRRESPECTIVE OF LOAD CHANGES OF SAIDPHOTOMULTIPLIER.